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E36 Coupe Window motor replacement

My driver's window had been doing the "up-stop-down" thing for a while and finally stopped working in the half down position. So I pulled the window regulator out and removed the motor (mine is the old style motor mounted behind the regulator plate structure) and gave them all a good disassemble and clean. The regulator was stuck stiff when I removed the motor but after days of applying penetrating lubricant to all the metal moving joints the thing would move freely as I would lift it off the bench. The motor was disassembled and heaps of black dust (probably from the magnet around the shaft) came out onto the bench.

I bought a new motor (67628360977) anyway from Schmiedmann in Denmark (it was US$140, so cheap affordable insurance for a NEW part) and some new sliding window connecting parts (51321938884, very cheap too) and the window is now operating in complete silence and the one-touch closing feature is all good. The old motor still worked after the clean and connecting to the wire loom in the door, so I've still got that as a future spare part. Hopefully all the removed dust has made it good again, but I think the freeing up of the regulator movement is the main fix.

The passenger door window has started the "up-stop-down" dance as well so I will at least do the same regulator lube and motor clean job on it.

I had the same situation with my 96 M3. I had the same symptoms and then a total freeze up of the motor. My regulator seemed to be okay but the motor wasn't able to move the window anymore. I took it apart as you did and found the black powdery gunk everywhere around the brushes. I think this is just from the brush wear in the motor. I cleaned the slipring and brushes with some solvent and redistributed the grease in the gears, but the ring gear had cupping wear from the worm gear, so I was skeptical. After reassembly it actually worked quite a bit better, I think cleaning out the commutator/brush assembly helped in that regard. Soon after though I began to hear gear slipping whenever the window would go to the full sealed position and finally it has become stuck shut. So I think if your internal gears are in good shape, cleaning the brushes may extend the life of the motor. Otherwise if the gears are worn it's anyone's guess. I'll be ordering a new motor soon.

Just looked at the passenger side and its regulator is rivetted in where as the driver's side had bolts and nuts. I know the driver's door has signs of re-painting so it must have been previously repaired but the passenger door must still be factory original.

I only lubed the passenger side regulator and replaced the window sliders, but the window still occasionally does the "up and down dance".

So I think tomorrow I'll attempt to remove the motor metal cover if I can get to the 2 back torx screws and give the motor a clean with a vaccum cleaner.
I think the "up and down dance" many be caused by the build up of the black dust and it stops the movement pulses being received by the window controller so it initiates the "something caught in the window" safety feature and reverses and stops the window movement.

At least on my Australian coupe model only the driver's door has the one-touch close feature so I can by-pass the "something caught in the window" safety feature by pressing the up button continuously in position 2 and the window closes fine. The one-touch open feature still works okay on the passenger side so there is really nothing wrong with the motor's operation, except perhaps for the movement pulse generation.

Good thing is I replaced the driver's side with a new motor as this is the window that I use the most.